No, Plan B STILL Doesn’t Impact Implantation


In preparation for all of the, “Obama wants to kill all the preshus babeez with the abortion pill! ELEVENTY!!11!!11” posts and tweets I knew I was invariably going to see today, I decided to go ahead and post this, in hopes that I’ll at least educate a person or two as to the facts about emergency contraception.

I hesitated to even write this post because I feel like I’m giving credence to the very idea, but I’ve grown weary of explaining all of this in several 140 character segments, so I thought I’d write it all out here in handy–dandy linkable blog form that I can throw out the next time some ill-informed under-educated anti starts spewing nonsense in my general direction.

If you’d like the quick and pretty version of how emergency contraception works, I highly recommend watching this utterly fantubulous video by @ASAPScience.

If you’d like a more in-depth look at how emergency contraception works, and particularly why emergency contraception packaging hasn’t quite caught up with the science, stick around to learn some more.

I decided to write this blog post after reading an article on claiming that “emergency ‘contraception’ can end the life of a unique human being,” and then really kicked myself into gear after the Obama administration’s decision last night to FINALLY do the right thing and abide by Judge Korman’s decision that emergency contraception should be available to child-bearing women and girls of all ages, without a prescription.

The main point of LifeNews’ article (and of the many, many, many similar stories floating around the antiverse) is that contraceptives, specifically emergency contraceptives (ECs), have a post-fertilization mechanism of action and are therefore killing the preshus, preshus babeez.

Now, I would say I can’t blame the antis for believing that ECs have such a post-fertilization effect – after all, it is listed that it is POSSIBLE on the packaging inserts of both Plan B and Ella, the two most-prescribed versions of emergency contraception pills in the US – however, it takes a special kind of deliberate, willful ignorance to ignore all of the data and information that I will be sharing below which solidly refutes this point, data which is, and has been, publicly available.

So, shall we begin our journey?

First, what IS emergency contraception?

Let me begin by saying what it is not. Emergency contraception is NOT an abortifacient. Let me repeat that: Emergency contraception is NOT an abortifacient.

Emergency contraception does not interfere with an established pregnancy – as defined by the USFDA/NIH and the American College of Obstetricians and Gynecologists as beginning with implantation of a fertilized egg – so it CANNOT be an abortifacient. Period. Full stop. Fin.

Emergency contraception IS a contraceptive method used to prevent a pregnancy from occurring following unprotected sexual intercourse (be it consensual or rape), or known or suspected contraceptive failure.

Emergency contraceptive methods include medications and IUDs (intrauterine devices), though as most of the debate around emergency contraception (EC) has centered around medication methods, this blog post will focus on emergency contraception pills (ECPs). There are various different types of pills, containing varied types and amounts of hormones, ranging from progestin only pills to higher doses of “regular” birth control pills. But, again, since most of the rancor against ECPs has been aimed at a particular form of ECPs (namely progestin-only methods), this post will focus on those.

The most well-known of the progestin-only methods ECPs, particularly in the US, is Teva Pharmaceuticals’ Plan B.

Plan B and Plan B One Step contain either two doses 750 μg of levonorgestrel to be taken twelve hours apart, or one does of 150mg of levonorgestrel. Plan B and Plan B One Step have been proven effective at preventing pregnancy when taken up to 72 hours following intercourse, though they are most effective when taken as soon as possible.

So how does emergency contraception work?

How (and whether) emergency contraception, specifically Plan B and Plan B One Step, works is dependent upon when during a woman’s menstrual cycle the medications are taken. If taken BEFORE ovulation, ECPs work to to inhibit the pre-ovulatory luteinizing hormone (LH) surge, preventing the follicles from developing / maturing and/or the ovaries from releasing an egg, thereby preventing fertilization (if there’s no egg for sperm to reach, there can be no fertilization of said egg).

THIS is the primary (and perhaps only) mechanism of action for ECPs. And, as I hope it’s clear, under this mechanism of action, it is IMPOSSIBLE for ECPs to impact a fertilized egg.

If taken AFTER ovulation, ECPs MAY work by impeding sperm function, thereby preventing fertilization, but more research is necessary to confirm this possible mechanism of action.

“But…but…Heather,” you say, “Plan B’s labeling and product packaging says it may also ‘inhibit implantation.'”

Why, yes, knowledgeable reader, it does. I’m proud that you took the time to look up the label for this medication. Unfortunately, a little knowledge can be a dangerous thing.

While the CURRENT label for Plan B states that medication may inhibit implantation by altering the lining of the endometrium, this label was approved by the FDA in 1999, when few (if any) studies had been conducted on possible post-fertilization effects of Plan B. Though Barr Pharmaceuticals – the original maker of Plan B, since purchased by Teva – did not request that implantation be included as a possible mechanism of action (and actually requested that it NOT be included) the FDA insisted it be included.

WHY was it included though? Well, the FDA has declined to comment on why Barr’s request that its original label omitting implantation as a mechanism of action was declined (citing confidentiality concerns), but it is likely that several factors played a role.

First, while the FDA recognized that Plan B was safe for use in preventing pregnancy, not enough data was available to definitively show that the medication did NOT impact fertilization as early studies were more focused on WHETHER Plan B was effective at preventing pregnancy, not on HOW it prevented pregnancy.

Second, because Plan B was the first progestin-only ECP, the FDA had no similar drugs from which to draw labeling requirements from. What the FDA DID do in drafting the labeling for Plan B was to look at the proposed Plan B label (which did not include implantation as a mechanism of action), FDA labeling guidance for progestin-only oral contraceptives, the label for Micronor (a norethindrone-based progestin-only oral contraceptive), the label for Ovrette (a levonorgestrel-based progestin-only oral contraceptive), and the labeling for PREVEN (an ECP containing both progestin and ethinyl estradiol).

Reviewing the labeling for these other drugs for guidance on the labeling for Plan B was (obviously) problematic, because none of the available drugs matched Plan B’s formula. While some studies had shown that oral contraceptives had been able to impact endometrial receptivity, it takes time for these effects to occur (it’s also important to note that these effects have not been shown to be significant enough to impact implantation). The 12 hours to 24 hours a woman would be exposed to the levonorgestrel on Plan B is simply not enough time for the drug to have any meaningful (if any) impact on the endometrium.

Finally, according to Dr. Gemzell-Danielsson, it may be possible that wishful thinking played a role –  i.e. some scientists, in thinking that if Plan B could also block implantation it would be more effective –  insisted, without any evidence, that it COULD block implantation.

So, in the absence of definitive proof that ECPs did NOT impact implantation, and faced with a myriad of previously approved oral contraceptive labels from which to draw upon, the FDA drafted a label and production information sheet for Plan B that included the following language:

How does Plan B® Work? Plan B® contains a dose of the hormone levonorgestrel that is higher than in a single birth control pill. Levonorgestrel has been used in birth control pills for over 35 years. Plan B® control pill to prevent pregnancy mainly by stopping the release of an egg from the ovary. It is possible that Plan B® preventing fertilization of an egg (the uniting of sperm with the egg) or by preventing attachment (implantation) to the uterus (womb), which usually occurs beginning 7 days after release of an egg from the ovary. Plan B® already attached to the uterus. The pregnancy will continue.



Emergency contraceptives are not effective if the woman is already pregnant. Plan B is believed to act as an emergency contraceptive principally by preventing ovulation or fertilization (by altering tubal transport of sperm and/or ova). In addition, it may inhibit implantation (by altering the endometrium). It is not effective once the process of implantation has begun.

Since 1999, however, many, many, many more studies have been conducted on the mechanisms of action for levonorgestrel ECPs, prompting the International Federation of Gynecology and Obstetrics (FIGO) and the International Consortium for Emergency Contraception to issue a statement that

Inhibition or delay of ovulation is LNG ECPs principal and possibly only mechanism of action. Review of the evidence suggests that LNG ECPs cannot prevent implantation of a fertilized egg. Language on implantation should not be included in LNG ECP product labeling.

Of the more recent studies:

The evidence is now conclusive that progestin-only ECPs such as Plan B do NOT have any impact on the implantation of a fertilized egg. So conclusive, in fact, that FDA spokespersons have admitted that, “The emerging data on Plan B suggest that it does not inhibit implantation. Less is known about Ella. However, some data suggest it also does not inhibit implantation” (Erica Jefferson) and “Data from studies in women on the mechanism of action of progestin-only drug products conclusively demonstrate that these products prevent ovulation and/or disrupt normal peri-ovulatory events resulting in ovulatory dysfunction. It is generally believed that this mechanism is responsible for most, if not all, instances in which emergency contraception prevents pregnancy.” (Steven Galson).

Further, the National Institutes of Health has removed any reference to the possibility of an implantation effect from its discussion of ECPs, and the Mayo Clinic has added the following wording to its page,

Morning-after pills do not end a pregnancy that has implanted. Depending on where you are in your menstrual cycle, morning-after pills may act by one or more of the following actions: delaying or preventing ovulation, blocking fertilization, or keeping a fertilized egg from implanting in the uterus. However, recent evidence strongly suggests that Plan B One-Step and Next Choice do not inhibit implantation. [emphasis added]

So, given this plethora of evidence, why hasn’t Plan B’s labeling changed?

Well, dear reader, that is an interesting question.

First, Teva absolutely CANNOT change the label on its own without FDA approval. Doing so could render the drug misbranded and an unapproved new drug.

According to the FDA, the process to change the label on a medication can be initiated either by the pharmaceutical manufacturer itself, or by the FDA. The FDA would not comment on ongoing application processes, citing confidentiality, so I contacted Teva. Sadly, I was informed by Denise Bradley, Teva’s Vice President of Corporate Communications for the Americas, that they, too, were unable to comment on their communications with the FDA due to confidentiality.

However, given that the FDA has recently encouraged Teva to submit an application to permit Plan B One Step to be sold OTC without age restrictions, it is not outside the realm of possibility that other efforts to make the medication more widely available to women (including those women who are discouraged from taken it by the mistaken belief that it may prohibit implantation) through making Plan B’s labeling scientifically and medically accurate are underway, or will shortly be underway.

Till next time,

– H

If you found this post informative, or educational, or witty, etc., you can click on the subscribe button just a few inches up and to your right to receive updates when I post on new womensy topics (you can unsubscribe at any time – I promise I won’t be offended). If you feel so inclined, you can also click the Donate button to help support the work I’m doing and keep me fighting the patriarchy. Thanks!

© Heather Parker and Antigone Awakens, 2012-2013.

2 thoughts on “No, Plan B STILL Doesn’t Impact Implantation

  1. Sherlock

    Thanks for this blog. I have been arguing all day with pundits, and the first thing they link to is “Plan B has the warning on their website! It is abortion!”


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s